The present invention relates to optical transmission lines used when optical signals are transmitted in parallel between and through devices, methods of making such optical transmission paths, and methods and devices for measuring their optical transmission times.
Japanese patent publication JP-A-64-48011 discloses a parallel data transmission optical cable which performs parallel transmission of data at high speed between computers and between computer terminals using a plurality of optical fibers.
This publication discloses the measurement of uneven optical path lengths of the respective optical fibers before a connector is attached, adjustment of the position of connector attachment such that the unevenness of the optical path lengths is less than 50 cm and then attachment of the connector. However, this publication does not disclose a specified optical path length measuring device and method. This publication is only directed to changes in the optical path length between connectors provided at the opposite ends of the optical fibers which constitute the optical cable and does not consider the respective absolute values of the optical path lengths of the optical fibers and the difference in optical path length between the optical cables.
When processing of data is made while transmitting/receiving data between and in the devices, an optical transmission path where not only unevenness of optical transmission times but also optical transmission times themselves are set is required. In addition, in order to increase the signal transfer speed, it is necessary to adjust with high accuracy the optical transmission time of the optical transmission path.